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• Second Quarter 1993 Monitoring and Sampling Report July 30, 1993 Southland Site No 20680, 9110 Thornton Road, Stockton, CA 3 System Groundwater monitoring was performed according to Groundwater Technology's Standard Operating Procedures (SOPs) Copies of the SOPs are included In Attachment 3 Analysis of the groundwater monitoring data Indicates that groundwater elevations In the monitoring wells at the site have decreased approximately 15 feet since the previous quarter's monitoring (April 2, 1993) As of June 30, 1993, the average groundwater elevation at the site was 3130 feet below mean sea level, and the average DTW at the site was 43 30 feet below grade Since the groundwater levels at the site were first monitored In May 1986, the local groundwater elevation has fluctuated seasonally and, In general, has steadily declined Groundwater monitoring wells MW-2 through MW-4 and MW-10 could not be monitored on June 30, 1993, because they were dry Monitoring wells MW-6 and MW-12 are no longer In service, and at Southland's direction, monitoring wells MW-11 and MW-i4 are no longer being monitored or sampled The well completion data and current status of the monitoring wells at the site are summarized In Table 2 A potentiometric surface map (Figure 2) was prepared using monitoring data collected on June 30, 1993 FIgure 2 indicates a groundwater flow direction generally to the east with a gradient of approximately 0 002 foot per foot MONITORING WELL SAMPLING AND ANALYTICAL RESULTS On June 30, 1993, groundwater samples were collected from monitoring wells MW-1, MW-5, MW-7 through MW-9, MW-13, MW-15A through MW-15C, MW-16, MW-17A through MWA7C, and MW-18 through MW-20, former pumping wells PW-1 through PW-3, and former recovery well RW-1 The status of all monitoring wells Is summarized in Table 2 Samples were collected according to Groundwater Technology's SOPs Before sampling, at least 4 well-casing volumes of groundwater were removed from each well by hand bailing unless the wells purged dry The groundwater was allowed to recover to at least 80 percent of the original static water level before sampling The groundwater samples were collected using an Environmental Protection Agency (EPA)-approved Teflon® sampler The samples were collected In laboratory- supplied containers, preserved, labeled, and stored on ice Samples were transported under chain- of-custody protocol to GTEL Environmental Laboratories, Inc a California-certified laboratory In Concord, California Each sample was analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons-as-gasoline (TPH-G) using modified EPA Methods 5030/8020/8015 With one exception, the analytical results of the samples collected on June 30, 1993, reported BTEX . and TPH-G concentrations below method detection limits (MDIs) The one exception was the 12118023 020 ULM GROUNDWATER a TECHNOLOGY, INC